On paper, a fuel pump replacement reads like a minor errand - right up until the car quits on a hot afternoon and won't restart. That situation carries a little extra weight for a 1970-73 240Z owner. Yutaka Katayama worked so hard to bring this car into American hands, and it deserves much better than a slow death at a busy intersection.
The mechanical pump that Nissan first fitted to the L24 engine is very great in its simplicity. The catch is that 50 years of heat cycles, ethanol-blended fuel and hardened rubber will wear down even the best original hardware. A cracked diaphragm or a sluggish check valve can mimic a dozen other problems, and it's one of the more time-consuming diagnostic detours that I see with this engine. Plenty of owners spend weeks chasing ignition faults or carburetor jets before the actual culprit is ever identified.
Factors like budget, originality, climate and how the car actually gets driven day to day all play into the right choice. A concours-correct show car has very different needs than a modified street driver with triple Webers and a full summer of track days. What works for one owner can be wrong for the next. And these cars have had decades to accumulate very different maintenance and storage histories, which alone can pull the answer in a whole different direction.
Fuel delivery is something that's very much worth doing right on a build like this. A reliable fuel system protects the engine, keeps the carburetors happy and honors the owner's investment in one of the most legendary Japanese sports cars ever imported to North America. The 240Z earned its reputation the hard way - the least we can do is keep it on the road where it belongs!
Let's talk about fuel pump options so you can choose with confidence!
Table of Contents
The Factory Pump Runs With No Wiring
The 240Z's mechanical fuel pump is about as low-tech as engine parts get, which is a big part of why it works - it mounts directly to the L24 cylinder head, and as the camshaft spins, it rocks a small arm back and forth. That arm flexes a rubber diaphragm inside the pump body (it's what draws the fuel forward from the rear tank) with no wiring and no external power source - nothing at all.
Nissan chose this design for an easy reason - it runs all on its own with zero outside assistance. No dedicated power wire to run, no relay to mount and no switch to flip. The engine itself is what drives the pump - it just does what it already does, which means one less electrical circuit in the whole setup to worry about. That simplicity is a big part of why most 240Z owners are pretty happy to leave the mechanical pump right where the factory put it.
No strange hum or buzz from under the car at idle. No pump module to wrestle out of the gas tank on a hot Saturday afternoon. And when something does eventually wear out, the parts are cheap and not hard to find, and the repair itself is pretty manageable for most home mechanics - even without a full shop setup.
This baseline needs to be right before you do anything else. A healthy mechanical pump on a well-maintained L24 will move fuel at a steady low pressure - just what the original SU carburetors were built for. The whole system was built to work together as a package, and that relationship still holds up well for a stock or mildly restored Z. The more you stray from the original setup, the more you have to account for what changes downstream - and those changes add up pretty fast.
Why Old Diaphragms and Valves Break Down
After fifty or more years of heat cycles, vibration and nearly steady fuel exposure, the factory mechanical pump on a 240Z is more or less working against you at this point. The diaphragm cracks, the check valves wear out, and the gaskets start weeping fuel right where they used to hold a tight seal. These are old parts (decades old), and they're going to act like it.
The Renewable Fuel Standard pushed refiners to blend ethanol into gasoline, and ethanol-blended fuel became the new normal within just a few years. That's bad news for 240Z owners - ethanol is hard on the original rubber parts inside the mechanical fuel pump, and those parts were never made to manage it. The wear accumulates slowly over time, usually long before there's any reason to suspect a problem.
Of all the ways a fuel pump can fail, the diaphragm is the part that's worth watching most closely. A small tear is enough to let fuel slip through the pump body and into the crankcase oil - and once that happens, the oil gets diluted and mostly loses its ability to protect the engine. A fuel smell from around the dipstick is usually your first sign, and it's not something to put off.
You can rebuild the original unit, drop in a replacement mechanical pump or move to a different setup altogether.
Heat Soak and the Hard Hot Start
The 240Z has its fuel tank mounted at the very back of the car, so the fuel has a pretty long trip to make before it ever reaches the engine. All that extra distance starts to work against you on a hot day.
When you shut off a hot engine, the heat has nowhere to go. It builds up inside the engine bay and radiates into everything around it (the fuel lines, the mechanical pump and the carbs). At some point, the fuel sitting in those lines gets warm enough to turn into vapor, and a vapor-filled line just can't feed the engine the way it needs to. Most Z owners who run into a hard hot-start are dealing with this.
The ethanol in modern pump gas can add another layer to this. It raises the vapor pressure of the gasoline it's blended into, so the fuel vaporizes quite a bit faster once the heat gets into the equation. The 240Z came from an era where ethanol-blended fuel wasn't common, and the fuel system was designed around that, so it struggles to manage what we're actually running through it.
To be fair, plenty of Z owners have had actual success with heat shields around the pump and with more careful fuel line routing - and both are well worth doing. The issue is that they work by cutting down on heat exposure, and there's only so much that insulation alone can do after a long drive on a brutally hot afternoon. You already know what I mean if you've ever sat in a parking lot waiting for your Z to cool down enough to restart.
Why Electric Pumps Push Rather Than Pull
Electric pumps have a benefit over mechanical ones against vapor lock, and it all traces back to something pretty basic - the direction that the fuel actually moves. A mechanical pump pulls fuel toward the engine. That pulling motion creates just enough low pressure in the line for vapor bubbles to sneak in. An electric pump does the opposite - it pushes a steady column of liquid fuel from behind. That forward pressure keeps the line full enough that vapor doesn't get a chance to form.
A few different setups are worth looking at depending on your situation. An in-tank pump lives directly inside the fuel tank, and that puts it about as close to the fuel source as you can get. An inline pump mounts on the outside of the tank but stays close to the rear of the car. A compact cube-style pump is another option for that same general area - it's small enough to fit into a tight spot, and it performs well even if you're working with limited space back there.
Nissan ran into this same choice in 1975 with the 280Z, and they went with factory fuel injection from day one. That meant an electric fuel pump came standard on the car. That alone tells you something about where automotive fuel delivery was already headed at the time.
A couple of points are worth flagging before we move on from electric pumps. First, they can get pretty loud (especially the older or budget-end models), so where you mount yours matters for both performance and how much noise bleeds into the cabin.
The second point has to do with height. A pump needs to sit low and close to the tank - you're asking for trouble if it ends up mounted high in the engine bay. Gravity works against it and the pressure drops, and before long you're right back to the same fuel delivery problems that you were trying to get rid of.
Get the Right Fuel Pump for Your Setup
Triple Weber DCOE carburetors and full fuel injection setups have a much higher fuel demand than a stock mechanical pump was ever designed to work with. A factory pump just doesn't have the flow capacity to keep up with either of the setups, and your engine will feel the fuel shortage immediately.
Pressure is only half of the fuel pump conversation. Flow rate is what keeps the engine fed all the way up through high rpm under load. A pump can hold steady pressure at a standstill and still come up short when the engine is working hard - that's where most builds run into issues.
Most triple Weber and fuel injection builds fall somewhere in the 30 to 60 gallons per hour range - and the exact number can vary based on displacement and how aggressively the tune has been pushed. At a minimum, it gives you a concrete target to shop toward, and that's a bit more helpful than just grabbing whatever looks decent on a spec sheet. A pump that's well-matched to what the engine needs will let it pull cleanly all the way to redline - smooth power delivery through the full rev range with no hesitation or stumble.
An oversized pump is a risky bet - a pump that pushes more pressure than your carburetors or injectors are rated for will just create a whole new set of problems. What you actually want is a matched system - pump output that lines up with what the rest of the fuel system was built to work with.
Pull up the flow and pressure specs for your carburetor or injection setup before buying anything - it only takes about 5 minutes.
The Right Fuel Pressure for Stock SU Carbs
The SU-style carburetors that came stock on the 240Z were designed to run at right around 2 to 3 PSI. Push past that range, and the float needle valves inside the carbs start to give up. Each of the valves has just one job - to shut off the fuel the second the float bowl fills up. With too much pressure working against them, they just can't hold the line anymore. The bowls flood, and at that point raw fuel is either spilling into the intake or dripping directly down onto the engine - and neither one is something that you want happening anywhere near a hot motor.
A fuel pressure regulator sits between the fuel pump and the carbs, and its whole job is to bring that pressure down to a level that the carbs can work with. The part itself is pretty simple - there isn't much going on inside it. Where it sits in the line does matter though - it needs to be close enough to the carbs that the pressure doesn't have a chance to drift before the fuel arrives.
A fuel pressure gauge is what turns a guessed-at fuel setup into one that's actually dialed in. With one in the system, you can watch the exact PSI that your carbs are seeing as it happens and make small adjustments until that needle holds steady right in the 2 to 3 PSI range. Without one, you're flying blind and just hoping that the regulator happened to land where it needs to be.
Some builders skip the gauge to save a few dollars or just to make the install a little cleaner. Fair enough - but raw fuel sitting near a hot engine has a tendency to make that shortcut look way less like a smart call.
A regulator and a gauge together will run you very little money compared to what a flooded carb or an engine fire will cost you.
Which Fuel Pump is Right for Your Z
A fresh mechanical pump is always the right move for a numbers-matching 240Z show car. It keeps everything under the hood period-correct and goes a long way toward protecting the car's resale value - something an aftermarket electric pump just can't replicate, no matter how clean the installation looks.
An electric pump is the better move for a driver or a modified build. It solves the heat-soak and flow problems we went over earlier, and it's just a much cleaner setup all around for any car that actually sees hard use.
One setup worth learning about is running both pumps at the same time. The idea is to leave the mechanical pump in place for originality and wire in a small electric pump to run as a secondary. It's about as solid a middle ground as you're going to get for a car that sees actual road miles but needs to look right under the hood at a show - and if your Z falls into that dual-use category, it's the option I'd point most driver-quality owners toward.
The pump is only part of the equation if you go electric - the wiring deserves every bit as much attention. A direct connection off the ignition switch pushes the full electrical load through the old factory wiring, and that's a problem waiting to happen on a car of this age. A dedicated relay with an inline fuse is the right move - it pulls that load off the ignition circuit and keeps the whole setup well protected.
An inertia cutoff switch or an oil-pressure cutoff switch is also worth adding to the mix so the pump will shut itself off automatically during a crash or a stall - neither of which is a moment when you would want fuel to still be flowing. And a block-off plate needs to go on right after the mechanical pump comes off the block to seal that port up tight.
Build Your Dream Car
When the research is done, and the right setup finally clicks into place, the effort is worth every hour that you put into it. A well-matched fuel system just does what it's supposed to - the Z fires up immediately, it pulls strong and smooth all the way through the rev range, and it won't leave you parked on the side of the road on a 95-degree day with nothing to do but wait for the engine to cool back down.
Most Z owners aren't chasing trophies or trying to put on a show for anyone - what they actually want is a car that fires on the first crank and reliably gets them home every time. That's a fair ask for a fifty-year-old sports car, and it's well within reach with the right fuel setup dialed in. A bit of patience on the front end is worth it when the end result is a car that you can count on day after day.
That same mindset (reliability, attention to detail and a genuine commitment to doing the job right) is what Skillard brings to its full lineup of custom Datsun parts. The catalog covers the 240Z, 260Z and 280Z, and whether you're in the middle of a full restoration or just want to make a few improvements along the way, there's a strong chance that you'll find what you're after. The range is wide ( bumpers, aluminum door cards, center consoles, spoilers and plenty more) and each piece is built to fit and work the way it should on a Z. And none of it is generic or off-the-shelf. Every part in the catalog was designed with these cars specifically in mind, and the quality does back that up.
Skillard.com has the full catalog up and ready - go and have a look and find the right pieces for your build.
